Saw some gameplay of it on twitch. Looked like a multiplayer mod for Space Marine. Its very much in a pre-alpha state overall.
You're not far off at all. I've been playing about two weeks so what I said above is accurate. Multiplayer mod, yes, it's Battlefield: Space Marine (though you may also call it a multiplayer mod for Battlefield lol),.
To be pedantic, I feel like it's in mid-alpha rather than pre-alpha. All all the Space Marine/Chaos resources are in and work, really. It is literally plays like Space Marine already, besides bugs and optimization. Weapons from Space Marine are there, Tacticals, Devs, Assault are there, and all three play at the same quality as in Space Marine. Just again with tweaks to weapon, bugs, and shitty optimization. In addition there are two new classes. Also again the APC/Rhino and Tank/Predator are in and they work quite well. There are already a few maps, and they're pretty decent - again Battlefield sized. Literally playing something like 20v20 on one map.
Now, I agree that it's quite still in alpha because there are no Eldar and Orks. That... is going to be trouble for getting out of alpha. And also is going to be a lot of trouble balancing that shit in beta.
Also I don't really play that much, I just got bored, so I'm just relaying facts not hyping anything. I sure as hell know they ain't gonna have a Planetside experience, and that they won't make any kind of Summer 2016 release. Of course, saying that it'll be released in Summer or super early is just common-place shit devs/producers say and don't really mean. It'll be delayed.
Hopefully it won't do that stupid Warmachine Tactics bulltshit where they are considering that they haven't even "launched the game yet."